Benefit Plans, Assumptions and Future Cash Flows (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended			12 Months Ended
	Dec. 31, 2010		Jun. 30, 2010	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Estimated future benefit payments [Abstract]
Minimum required contribution				0
Pension Benefits [Member]
Projected benefit obligation [Abstract]
Discount rate (a)	5.55%	[1]		4.86%	[1]	5.55%	[1]	5.80%	[1]
Rate of compensation increase	4.50%			4.50%		4.50%		4.57%
Net periodic benefit expense: [Abstract]
Discount rate (a) (b)				5.55%	[1],[2]	5.80%	[1],[2]	6.28%	[1],[2]
Rate of compensation increase				4.50%		4.57%		4.59%
Expected long-term return on plan assets (c)				7.25%	[3]	7.50%	[3]	8.50%	[3]
Estimated future benefit payments [Abstract]
2012				$ 49
2013				48
2014				51
2015				56
2016				58
2017-2021				321
Other Postretirement Benefits [Member]
Projected benefit obligation [Abstract]
Discount rate (a)	4.38%	[1]		3.76%	[1]	4.38%	[1]	6.36%	[1]
Rate of compensation increase	0.00%			0.00%		0.00%		0.00%
Net periodic benefit expense: [Abstract]
Discount rate (a) (b)	4.64%		6.36%	4.38%	[1],[2]	5.50%	[1],[2]	6.14%	[1],[2]
Rate of compensation increase				0.00%		0.00%		0.00%
Expected long-term return on plan assets (c)				0.00%	[3]	0.00%	[3]	0.00%	[3]
Assumed health care cost trend rates [Abstract]
Health care cost trend rate assumed for next year				8.00%		8.50%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)				4.80%		4.50%
Year that the rate reaches the ultimate trend rate	2018			2024		2018
Effect of one-percentage point change in assumed health care cost trend rates [Abstract]
Effect of one-percentage-point increase on total of service and interest cost components				0.2
Effect of one-percentage-point decrease on total of service and interest cost components				(0.2)
Effect of one-percentage-point increase on postretirement benefit obligation				1
Effect of one-percentage-point decrease on postretirement benefit obligation				(1)
Estimated future benefit payments [Abstract]
2012				10
2013				12
2014				10
2015				10
2016				11
2017-2021				$ 53

[1] We determine the discount rate primarily by reference to the effective yields on high quality corporate bonds that have a comparable cash flow pattern to the expected payments to be made under our plans.

[2] As a result of the changes to other postretirement benefits during the second quarter of 2010, we remeasured our postretirement obligation as of June 30, 2010. The discount rate used to determine the net periodic benefit expense was 6.36% for the six months ended June 30, 2010, and 4.64% for the six months ended December 31, 2010.

[3] The expected return on plan assets reflects the weighted-average of the expected long-term rates of return for the broad categories of investments held in the plans. The expected long-term rate of return is adjusted when there are fundamental changes in expected returns on the plan’s investments.